C / C++ / MFC

1-Jun-06 19:19

Hi,
I have the file named "mobi.avi",

I used fopen() with the prama mode is "w+" to open this file for my checking in my function, but while this file is opening by the orther program as Window Media then the function will show the error is file can not access. But my problem is when I stop play the file with Window Media, the file removed.

So, I want to ask you how can i do with not remove the file when open error,

Please help me!

Thank in advacnce

kakan1-Jun-06 19:30

1-Jun-06 19:30

<edit>
In general, try MSDN for this kind of problems (and heaps of other information).
http://msdn1.microsoft.com/en-us/default.aspx[^]

From MSDN:

The character string mode specifies the type of access requested for the file, as follows:

"r"

Opens for reading. If the file does not exist or cannot be found, the fopen call fails.

"w"

Opens an empty file for writing. If the given file exists, its contents are destroyed.

"a"

Opens for writing at the end of the file (appending) without removing the EOF marker before writing new data to the file; creates the file first if it doesn’t exist.

"r+"

Opens for both reading and writing. (The file must exist.)

"w+"

Opens an empty file for both reading and writing. If the given file exists, its contents are destroyed.

"a+"

Opens for reading and appending; the appending operation includes the removal of the EOF marker before new data is written to the file and the EOF marker is restored after writing is complete; creates the file first if it doesn’t exist.

When a file is opened with the "a" or "a+" access type, all write operations occur at the end of the file. The file pointer can be repositioned using fseek or rewind, but is always moved back to the end of the file before any write operation is carried out. Thus, existing data cannot be overwritten.

Probably you want to use "r"

huutribk20011-Jun-06 20:09

1-Jun-06 20:09

I used "r" param but with this I can not check if the file is opening or not.
When the file is opened by orther app as window media, I want to check this and let user know the error message, but when i close window media then the file is deleted. How way to don't let app delete automatic when use fopen function?

The follow code i tried:

	FILE * file = fopen(m_szFileName, "r");
	if (NULL != file) 
	{
	  if(remove(m_szFileName)){
		strcpy(m_szErrorMessage, "SetRecordFileName(): File    access error! Please check and try again!");
		return (false);		
	  }
	}

FILE* file = fopen(m_szFileName, "w");
	if (NULL == file) 
	{
	  strcpy(m_szErrorMessage, "SetRecordFileName(): File access error! Please check and try again!");
	  return (false);
	}

kakan1-Jun-06 20:25

1-Jun-06 20:25

OK, then I got your problem. Blush | :O

You might consider to use the Win32-function CreateFile instead. And set share mode for exclusive access, like this:
CreateFile("TheFile"
GENERIC_READ, // access (read-write) mode
0, // share mode (exclusive access)
NULL, // pointer to security attributes
OPEN_EXISTING, // how to create
FILE_ATTRIBUTE_NORMAL, // file attributes
NULL // handle to file with attributes to copy
);

Then you should get an error if the file is opened by someone else, since th file cannot be opened for exclusive access.

huutribk20011-Jun-06 21:08

1-Jun-06 21:08

I used at below but it still delete the file after show the error message and close the Window media, this seem to the same above problem:
Can you help again?
--------------------

	HANDLE hFile =CreateFile(m_szFileName,GENERIC_READ, // access (read-write) mode
	FILE_SHARE_READ, //Also try with 0 //share mode (exclusive access)
	NULL, // pointer to security attributes
	OPEN_ALWAYS, // how to create
	FILE_ATTRIBUTE_NORMAL, // file attributes
	NULL // handle to file with attributes to copy
	);
	
	if(INVALID_HANDLE_VALUE == hFile){
		strcpy(m_szErrorMessage, "SetRecordFileName(): File access error! Please check and try again!");
		return (false);		
		
	}else{
		CloseHandle(hFile);
	}

kakan1-Jun-06 21:50

1-Jun-06 21:50

The file is opened for reading (only), this CreateFile call can never delete the file as long as you use GENERIC_READ.

But I do suggest you to:
1.
Use OPEN_EXISTING instead of OPEN_ALWAYS. (The file already exists, doesn't it?)

2.
Use share mode 0 for exclusive access.

huutribk20011-Jun-06 22:04

1-Jun-06 22:04

If I used OPEN_EXISTING and share mode 0, but I can not create a new file if the file have not existed,
My function is record a file avi,
if the file have not existed then create new one,
if the file existed and have not opened by orther app then over write this,
if the file existed and opened by orther app then give the user error is can not access and do nothing.

Any help again?

Thanks again!

kakan1-Jun-06 22:32

1-Jun-06 22:32

That's a different story!

I suggetst you to do like this:
Open the file for reading, exclusive access. Then you will know two things:
A.
The file exists.
B.
The file is not opened by some other application.
Close the file, if it's open.

If you get an error, then examine the error. If you get ERROR_ACCESS_VIOLATION (?) then the file exists but is opened by some other application. Show user error and terminate the function.

If you get an error meaning that the file doesn't exist, then create a new file. (CreateFile, GENERIC_WRITE, maybe exclusive access).

I think that should do it.

huutribk20011-Jun-06 23:13

1-Jun-06 23:13

Hi,

HANDLE hFile =CreateFile(m_szFileName,GENERIC_READ, // access (read-write) mode
0, // share mode (exclusive access)
NULL, // pointer to security attributes
OPEN_EXISTING, // how to create
FILE_ATTRIBUTE_NORMAL, // file attributes
NULL // handle to file with attributes to copy
);

I can not get the case as above(A and B), the hFile HANDLE always is 0xffffff when the file not existed and the file opened by orther function (always is INVALID_HANDLE_VALUE for tow case),
the constant ERROR_ACCESS_VIOLATION had not defined.

How way to recognize what the error happends with CreatFile function?
Any help again?

kakan1-Jun-06 23:43

1-Jun-06 23:43

Use GetLastError()

huutribk20014-Jun-06 18:57

4-Jun-06 18:57

Hi,
I still have problem with deleting file.
I did as below:

HANDLE hFile =CreateFile(m_szFileName,GENERIC_READ, // access (read-write) mode
	0, // share mode (exclusive access)
	NULL, // pointer to security attributes
	OPEN_EXISTING, // how to create
	FILE_ATTRIBUTE_NORMAL, // file attributes
	NULL // handle to file with attributes to copy
	);

	DWORD lerr =0;
	lerr=GetLastError();
	
	if(INVALID_HANDLE_VALUE == hFile){
		if(lerr==ERROR_ACCESS_DENIED){
		fclose(logFile);
		 strcpy(m_szErrorMessage, "SetRecordFileName(): File access error! Please check and try again!");
		 return (false);		
		}
	}else{

		//Create new file
	}


This show the error when the file opened by orther appp but it still be deleted when the app close.

Any help again??

Many thank!

huutribk20014-Jun-06 21:19